I EV per Torr*cm -- What does it mean?

[DariusP]

I was reading about this
https://en.wikipedia.org/wiki/Nitrogen_laser

and it says "80 to 100 eV per Torr*cm pressure of nitrogen gas". I'm finding this a little bit confusing. It needs some specific amount of energy in a centimeter of volume with 1 Torr of pressure?

 

[Cutter Ketch]

I don’t see that in the article, but I can explain the unit.

That is an ionization constant. See the wiki article on Paschen’s Law:
https://en.m.wikipedia.org/wiki/Paschen's_law
This constant relates the electric field strength to the energy per collision required to cause ionization and so sustain a discharge. The pressure is in there because the energy accumulated by a particle depends on the distance over which it is accelerated by the field, so the energy per collision depends on the mean free path length which is inversely proportional to the pressure.

Note that for a laser this constant is not necessarily for the minimum energy for discharge, but sets the energy per collision high enough to excite the lasing state.

 

[DariusP]

I don’t see that in the article, but I can explain the unit.

That is an ionization constant. See the wiki article on Paschen’s Law:
https://en.m.wikipedia.org/wiki/Paschen's_law
This constant relates the electric field strength to the energy per collision required to cause ionization and so sustain a discharge. The pressure is in there because the energy accumulated by a particle depends on the distance over which it is accelerated by the field, so the energy per collision depends on the mean free path length which is inversely proportional to the pressure.

Note that for a laser this constant is not necessarily for the minimum energy for discharge, but sets the energy per collision high enough to excite the lasing state.

Love you, thank you very much

 

[olgerm]

it is in surface area units. In SI units it is
eV per Torr*cm=$\frac{q_e*V}{Torr*cm}=\frac{1.60217646*10^{-19}*C*V}{133.322*Pa*m/100}=\frac{1.60217646*10^{-17}*C*V}{133.322*N/m}=1.2017344924318567*10^{-19}*m^2$